In this report, we present a vertical memristor based on a layered FePS3 two-dimensional material with the structure Ag/FePS3/Au, where FePS3 is a single-crystalline layer with a thickness of ∼151 nm. By operating a device with a pulse voltage of 0.1 V dual modes of resistive switching with both analog and digital features are implemented in a single device. One mode lies between the OFF and ON states and another lies in the ON state. The device shows nonvolatility. Short-term plasticity and long-term potentiation are observed. Therefore, the FePS3 memristor is suitable for application in flexible and complex neuromorphic systems.

In optical sensors and imagers, high gain that leads to high sensitivity and high signal to noise ratio (SNR) is often desirable. One popular approach is avalanche photomultiplication initiated by impact ionization in an avalanche photodiode or similar devices and the other approach is active pixel sensor (APS) with in-pixel amplifier. However, the former requires high electric field which induces high shot noise and the latter needs a multiple-transistor pixel circuit which compromises the fill factor and consequently, reduces the SNR. This work proposes and summarizes our recent efforts taken to achieve high gain optical sensors through subthreshold operation of photodiode-gated transistors.

A hybrid active pixel optical sensor for highresolution and high-sensitivity imaging is proposed and experimentally demonstrated. The sensor vertically integrates an amorphous silicon p-i-n photodiode and a low-temperature polycrystalline silicon readout thin-film transistor (TFT). The vertical integration results in a high fill factor (> 70%) and an enlarged photosensing area in the pixel. In the photodiode-gated TFT structure of the sensor, the output current is amplified by operating the TFT in the sub-threshold regime. A weakly wavelength-dependent photoconductive gain > 10 is obtained at visible wavelengths, enabling large area low-level light detection.

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A hybrid optical sensor that is merged with the display driving, low-temperature polysilicon thin-film transistor (TFT) is reported. The sensor achieves a fill factor >70% and a photoconductive gain > 10 3 %, which provides a promising solution for in-display fingerprint identification.